The benefits of endoscopic submucosal dissection (ESD) for colorectal lesions regarding curative resection and recurrence rates are well known. However, colonic ESD remains technically challenging, thus restricting its possible applications. Underwater-ESD uses the buoyancy effect of submerging the lesion under saline and the power of the water jet to open the submucosal space and has been used successfully to facilitate ESD in several regions. Nevertheless, evidence regarding its application for colonic lesions is still low.

Aim of this study is to evaluate the outcomes of underwater-ESD for colonic lesions in a prospective, multicenter setting. 

All consequent colonic lesions >20mm qualifying for endoscopic resection referred to the participating centers (Charite Universitätsmedizin Berlin, Bochum University Hospital, Augsburg University Hospital) were screened for inclusion in the study. An informed consent was acquired by all participating patients. The ESD procedure was performed under saline and according to the standards of each participating center. Primary endpoints were en bloc resection and histologically complete (R0) resection rates. Secondary endpoints included duration of the procedure, adverse events and recurrence rates in the 6- and 12-months follow-up.

53 consequent patients (36 male and 17 female) were included in our study. Average age was 66.8 years. 28 lesions were located in the right hemicolon, 10 in the left and 15 in the sigmoid colon. Median size of the lesions was 35mm (range: 20-115mm). 6 lesions were recurrent after previous endoscopic mucosal resection and 12 lesions were characterized as suspicious for malignancy. All lesions were successfully resected as ESD and all resections were en bloc and macroscopically complete. Internal traction was used in 18 cases. The flap technique was used in 40 cases, the pocket creation method in 12 and 1 lesion was resected with a combination of both techniques. Median duration of the ESD was 99 min. In 43 cases the ESD procedure was performed completely under saline. In the remaining 10 cases a part of the procedure (ranging between 20-50%) had to be performed under gas insufflation because of inadequate exposure or bleeding. Intraoperative adverse events included 7 bleedings, 6 superficial injuries of the M. propria layer and 1 perforation, all of which were successfully treated endoscopically. There were no delayed bleedings or perforations. Histological examination showed an adenoma in 45 cases (25 with low-grade and 20 with high-grade intraepithelial neoplasia) and a carcinoma in 8 cases (6 pT1sm1, 1 pT1sm3 and 1 T2). A histologically complete resection was confirmed in 49 cases (92%) and 51 resections were curative (96%). At the time of submission of this abstract 20 patients had completed the 6-months follow-up and there were no cases of recurrence.

Underwater-ESD is a safe and effective therapeutic option for the resection of colonic lesions, combining high rates of complete and curative resection with an improved safety profile.